Ingress protection for electrosurgical pencil switch

ABSTRACT

A surgical instrument includes a switch base, a power bus coupled to the switch base, an electrical lead coupled to the power bus, an actuator operatively engaged with the power bus, an actuator operatively engaged with the power bus, a membrane, and a housing. The switch base has top, bottom, and side surfaces. The membrane is disposed over the top surface of the switch base and over the power bus to seal the top surface of the switch base. The housing defines proximal and distal ends and a switch base cavity between the proximal and distal ends. The housing includes bulkheads that form a plurality of fluid impermeable seals that are disposed adjacent one of the proximal and distal ends. The fluid impermeable seals are configured to deter fluid from penetrating a proximal portion of the switch base cavity within which the electrical lead is coupled to the power bus.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of, and priority to, U.S.Provisional Patent Application Nos. 62/053,981 and 62/053,992, both ofwhich were filed on Sep. 23, 2014. This application is related to U.S.patent application Ser. No. 14/857,913, filed on Sep. 18, 2015, now U.S.Pat. No. 9,986,984. The entire contents of each of the aboveapplications are hereby incorporated herein by reference.

BACKGROUND

1. Technical Field

The present disclosure relates to medical devices and methods ofmanufacturing the same. Specifically, to present disclosure relatesfluid ingress protection in a surgical instrument and methods forassembling the same.

2. Discussion of Related Art

Electrosurgical medical devices have become widely used by surgeons.Electrosurgical medical devices may include a hand-held instrument,e.g., pencil, which transfers radio-frequency (RF) electrical energy toa tissue site from a suitable electrosurgical generator. The electricalcurrent may be returned to the source via a return electrode padpositioned under a patient, or a smaller return electrode positioned inbodily contact, with or immediately adjacent to, the surgical site. Thewaveforms which result from the RF electrical current may be used toproduce a variety of effects, depending on the power applied, and thefrequency used. These effects include surgical cutting, coagulation,cauterization, or sealing.

As electrosurgical pencils are, even when assembled by humans,relatively small and simple devices, and used by medical professionalsunder circumstances which may benefit from a “disposable” tool,electrosurgical pencils have become less expensive to produce. However,like most manufactured items, and all medical tools (especiallyinexpensive medical tools), the cost of manufacture, and thedistribution of electrosurgical pencils, along with the necessity torepurchase such “disposable” tools as they are discarded, adds greatlyto their overall cost to the surgical profession and, ultimately, totheir patients and health care costs. What is needed, then, is an evenless resource intensive method of manufacturing electrosurgical pencils.The savings in resources may be achieved at the stage where theelectrosurgical pencil switch circuitry is loaded into the moldedinsulative holding and positioning body of the electrosurgical pencilhand piece. Further savings may be achieved if a very low cost handpiece, which may be discarded after use, is matched with high qualityelectrical conductors (leading from the hand piece back to thegenerator), which may be retained and reused.

SUMMARY

In an aspect of the present disclosure, a surgical instrument includes aswitch base, a power bus coupled to the switch base, an electrical leadcoupled to the power bus, an actuator operatively engaged with the powerbus, a membrane, and a housing. The switch base has top, bottom, andside surfaces. The membrane is disposed over at least the top surface ofthe switch base and over the power bus sealing the top surface of theswitch base. The housing defines a proximal opening, and a switch basecavity between the proximal and distal ends. The housing includes aplurality of bulkheads forming a plurality of fluid impermeable sealsdisposed adjacent to at least one of the proximal or distal ends. Thefluid impermeable seals are configured to deter fluid from penetrating aproximal portion of the switch base cavity within which the electricallead is coupled to the power bus.

In aspects, the plurality of bulkheads includes upper bulkheads thatextend from the housing. Each of the upper bulkheads may engage themembrane to form one of the plurality of fluid impermeable seals. Theupper bulkheads may engage the membrane to form a secondary fluidimpermeable seal between the membrane and a portion of the switch basecavity.

In some aspects, the membrane is disposed over the top surface and aportion of each of the side surfaces of the switch base. The membranemay be disposed entirely over each of the side surfaces and portions ofthe membrane may be disposed over portions of the bottom surface of theswitch base.

In certain aspects, the membrane and the plurality of bulkheads preventa fluid from contacting the switch base.

In particular aspects, the surgical instrument includes a cableenclosing at least one electrical lead and passing through at least oneof the plurality of bulkheads. The cable may be mechanically coupled tothe switch base. The cable may pass through at least one of theplurality of bulkheads positioned adjacent a proximal end of the switchbase which forms one of the plurality of fluid impermeable seals withthe cable. The plurality of bulkheads may include a proximal openingbulkhead positioned adjacent the proximal end of the switch base whichforms one of the plurality of fluid impermeable seals with the cable.

In some aspects, the power bus includes an electrode connector extendingproximally therefrom. The electrode connector defining an electrodeopening that is configured to receive an electrode. The housing mayinclude an electrode connector bulkhead disposed between the distalopening and the switch base that forms a fluid impermeable seal with theelectrode connector.

In some aspects, the housing includes distal upper and lower bulkheadsthat form a fluid impermeable seal. The distal upper and lower bulkheadsmay form a fluid impermeable seal with the switch base.

In aspects, the housing includes a first housing portion and a secondhousing portion that are joined along mating surfaces. The matingsurfaces may be substantially parallel to a longitudinal axis of thehousing. The first housing portion may include a first half of at leastone of the plurality of bulkheads and the second housing portion mayinclude a second half of the at least one of the plurality of bulkheads.

In some aspects, the housing defines the actuator opening through anouter surface thereof. The actuator opening may be in communication withthe switch base cavity. The actuator may be disposed within the actuatoropening.

In another aspect of the present disclosure a surgical instrumentincludes a switch base, a power bus coupled to the switch base, amembrane, and a housing. The switch base has top, bottom, and sidesurfaces. The membrane is disposed over at least the top surface of theswitch base and over the power bus to seal the top surface of the switchbase. The housing defines a proximal opening, a distal opening, anactuator opening, and a switch base cavity including upper and lowerportions. The housing includes a plurality of bulkheads that form aplurality of fluid impermeable seals that are disposed adjacent to atleast one of the proximal, distal, or actuator openings. The fluidimpermeable seals are configured to deter fluid from penetrating theswitch base cavity.

In some aspects, the plurality of bulkheads includes upper bulkheadsextending form the housing adjacent the actuator opening. Each of theupper bulkheads may engage the membrane to form one of the plurality offluid impermeable seals.

In certain aspects, the membrane is disposed over the top surface and aportion of each of the side surfaces of the switch base.

In particular aspects, the surgical instrument includes a cableenclosing an electrical lead. The cable may pass through one of theplurality of bulkheads and extend through the proximal opening of thehousing. The cable may pass through one of the plurality of bulkheadspositioned adjacent a proximal end of the switch base which forms one ofthe plurality of fluid impermeable seals with the cable. The pluralityof bulkheads includes a proximal opening bulkhead that is positionedadjacent the proximal opening and forms one of the plurality of fluidimpermeable seals with the cable. The plurality of bulkheads may includea distal lower bulkhead and an electrode connector bulkhead that isdisposed between the distal opening and the distal lower bulkhead. Thedistal lower bulkhead and the electrode connector bulkhead form one ofthe plurality of fluid impermeable seals with an electrode connectorthat extends proximally from the power bus.

In yet another aspect of the present disclosure, a method of assemblinga surgical instrument includes coupling a power bus to a switch basethat has a top, a bottom, and side surfaces; adhering a membrane to thetop surface of the switch base over the power bus to form a switch baseassembly; positioning the switch base assembly within a first portion ofa switch base cavity defined by a lower housing portion; and joining thelower housing portion with an upper housing portion. The upper housingportion defines a second portion of the switch base cavity and theswitch base is disposed within the first portion of the switch basecavity. Joining the upper and lower housing portions together preventsfluid from penetrating a proximal portion of the switch base cavitywithin which an electrical lead is coupled to the power bus.

In aspects, joining the lower housing portion with the upper housingportion includes engaging portions of the membrane adhered to each ofthe side surfaces of the switch base with walls of the first and secondportions of the switch base cavity to form a fluid impermeable seal.Joining the lower housing portion with the upper housing portion mayinclude forming proximal and distal lower bulkheads that together definethe switch base cavity therebetween. Each of the proximal and distallower bulkheads may engage and form a fluid impermeable seal with theswitch base. Joining the lower housing portion with the upper housingportion may include applying adhesive, sonic welding, or laser welding.

In some aspects, the method includes positioning an actuator within anactuator opening that is defined by the second housing portion. Theactuator opening may be in communication with the switch base cavity.The method may include electrically coupling a cable to the power bus.

In certain aspects, joining the lower housing portion with the upperhousing portion includes engaging the membrane with upper bulkheads thatextend from the upper housing portion towards the lower housing portionto form a fluid impermeable seal with the membrane. Engaging themembrane with the upper bulkheads may include compressing the membraneagainst the switch base.

In still yet another aspect of the present disclosure, a method ofassembly a surgical instrument includes coupling a power bus to a switchbase that has a top, a bottom, and side surfaces; adhering a membrane tothe top surface of the switch base over the power bus to form a switchbase assembly; positioning the switch base assembly within a firstportion of a switch base cavity defined by a lower housing partition;and joining the lower housing portion with an upper housing portion thatdefines a second portion of the switch base cavity. The switch base isdisposed within the first portion of the switch base cavity such thatfluid is prevented from penetrating the first portion of the switch basecavity.

In some aspects, joining the lower housing portion with the upperhousing portion includes engaging portions of the membrane adhered toside surfaces of the switch base with walls of the first and secondportions of the switch base cavity to form a seal. Joining the lowerhousing portion with the upper housing portion may include formingproximal and distal switch base bulkheads that define the switch basecavity therebetween. The proximal and distal switch base bulkheads mayengage and form a seal with the switch base. Joining the lower housingportion with the upper housing portion may include applying adhesive,sonic welding, or laser welding. Joining the lower housing portion withthe upper housing portion may include engaging the membrane with switchprotrusions that extend from the upper housing portion towards the lowerhousing portion to form a seal with the membrane. Engaging the membranewith the switch protrusions may include comprising the membrane againstthe switch base.

In certain aspects, the method may include positioning a switch within aswitch opening that is defined by the upper housing portion. The switchopening may be in communication with the switch base cavity.

In particular aspects, the method may include electrically coupling apower cable to the power bus.

The assembly of the presently disclose electrosurgical pencil reducesthe cost of manufacture by eliminating hand labor during the assembly ofthe electrosurgical pencil. The design of electrosurgical pencil allowsthis by forming a seal between the exposed switch and other electricalcomponents, which allows for complete machine assembly. This savessignificant manufacturing costs, which results in the saving unnecessarycosts for the surgeon and savings to the patient.

Further, to the extent consistent, any of the aspects described hereinmay be used in conjunction with any or all of the other aspectsdescribed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

Various aspects of the present disclosure are described hereinbelow withreference to the drawings, wherein:

FIG. 1 is a perspective view of an exemplary electrosurgical systemincluding an electrosurgical pencil in accordance with the presentdisclosure;

FIG. 2 is an exploded view showing the components of the electrosurgicalpencil of FIG. 1 in accordance with the present disclosure; and

FIG. 3 is a side cross-sectional view taken along the longitudinal axisof the electrosurgical pencil of FIG. 1 in accordance with the presentdisclosure.

DETAILED DESCRIPTION

Embodiments of the present disclosure are now described in detail withreference to the drawings in which like reference numerals designateidentical or corresponding elements in each of the several views. Asused herein, the term “clinician” refers to a doctor, a nurse, or anyother care provider and may include support personnel. Throughout thisdescription, the term “proximal” refers to the portion of the device orcomponent thereof that is closest to the clinician and the term “distal”refers to the portion of the device or component thereof that isfarthest from the clinician.

The present disclosure provides for electrosurgical devices (e.g.,pencils) and methods for assembling the same. The presently disclosedelectrosurgical devices are configured to be assembled in automatedmanner or with minimal manual labor while sealing the electricalcomponents within the housing and preventing fluid and othercontaminants from contacting into the electrical components. Theelectrosurgical device according to the present disclosure includes amembrane disposed over electrical components of the device, (e.g.,switch base and power bus), which in turn is disposed within a housingincluding a plurality of bulkheads. The combination of the membrane andthe bulkheads provide for a fluid impermeable seal for the electricalcomponents of the device. As used herein, the term “fluid impermeable”includes fluid resistant or fluid proof and denotes making theelectrical components impervious to fluids and any other contaminants.

Referring now to FIG. 1, an exemplary embodiment of an electrosurgicalsystem 100 in accordance with the present disclosure is shown andincludes an electrosurgical pencil 10, an electrosurgical generator 110,and an electrode 120. The generator 110 is configured to provideelectrosurgical energy to the pencil 10 allowing the pencil 10 tocoagulate, ablate, or otherwise treat tissue. The generator 110 includesa receptacle 112 or a cable (not shown) to connect to the pencil 10 asdetailed below. In embodiments, the pencil 10 is a monopolar pencilincludes an active electrode 120 and the generator 110 includes a returnelectrode or pad 114 that is placed in contact with a patient during useof the pencil 10. It is also contemplated that the pencil 10 may be abipolar pencil including a return electrode.

Referring to FIGS. 2 and 3, the pencil 10 includes a first or upperhousing portion 20 a and a second or lower housing portion 20 b that arecoupled together to form a housing 20 (FIG. 1), which defines alongitudinal axis A-A. The housing portions 20 a, 20 b are coupledtogether along mating surfaces 24 a, 24 b that are substantiallyparallel to the longitudinal axis A-A to form a seal along the matingsurfaces 24 a, 24 b. The housing portions 20 a, 20 b may be coupledtogether by applying adhesive, sonic welding, laser welding, or anyother suitable methods.

The housing portions 20 a, 20 b together define a proximal opening 22, adistal opening 38, and a tortuous path 21 therebetween. The tortuouspath 21 includes a proximal switch base bulkhead 26 and a distal lowerbulkhead 32 defining a switch base cavity 27 therebetween.

With continued reference to FIGS. 2 and 3, the pencil 10 includes aswitch base assembly 12 positioned within the switch base cavity 27 anda power cable 14 passing through the proximal opening 22, which iscoupled to the switch base assembly 12. The switch base assembly 12includes a switch base 40, a power bus 50, and a flexible membrane 60.

The switch base 40 may be constructed of a nonconductive material (e.g.,thermoplastics, ceramics, and dielectric polymers). The switch base 40has a distal end surface 41, a top surface 42, a bottom surface 44, sidesurfaces 46, and a proximal end surface 49. The top surface 42 definesbus openings 43 (FIG. 2) for receiving portions of the power bus 50. Theproximal end surface 49 defines a connector opening 45 adjacent aproximal end of the switch base 40. The side surfaces 46 may definecutouts 47 adjacent the top surface 42.

The power bus 50 is coupled to the top surface 42 of the switch base 40and is constructed of a conductive material (e.g., copper, silver, gold,stainless steel, various alloys and combinations thereof). The power bus50 may be stamped from a single piece of conductive material. The powerbus 50 includes prongs 52, switch contacts 54, and an electrode contact58. The power bus 50 may include side protrusions 53 extending into thecutouts 47 of the switch base 40. The side protrusions 53 align thepower bus 50 with the switch base 40 and may secure the power bus 50 tothe switch base 40. In embodiments, the side protrusions 53 captureportions of the switch base 40 therebetween to secure the power bus 50to the switch base 40.

An electrode 120 (FIG. 1) is coupled to the electrode contact 58 of thepower bus 50. The electrode contact may define an electrode opening 59that frictionally receives the electrode 120 (FIG. 1). The electrodecontact 58 extends through the distal lower bulkhead 32 from the switchbase 40. The tortuous path 21 includes the electrode bulkhead 34, suchthat the electrode contact 58 may pass through and form a fluidimpermeable seal with the electrode bulkhead 34.

Each of the prongs 52 extends into a respective bus opening 43 toelectrically engage a respective lead 19 of cable 14 to create aninsulated displacement connection with the respective lead 19. Each ofthe switch contacts 54 has a non-activated position and an activationposition. In the non-activated position, a conductive path is broken andin the activated position, a conductive path is formed between thecorresponding prong 52 and the electrode contact 58. When a conductivepath is formed, energy is permitted to pass from the generator 110 tothe electrode contact 58.

With reference to FIGS. 1-3, the power cable 14 includes a proximal end15 (FIG. 1), a distal end 18, and a sheath 17 therebetween. The proximalend 15 includes a plug 16 (FIG. 1) that releasably couples to thegenerator 110 (e.g., the plug 16 is received within the receptacle 112of the generator). The distal end 18 includes connectors or leads 19that insert into the connector opening 45 (FIG. 3) of the switch base 40such that each of the leads 19 is positioned within one of the busopenings 43.

The bottom surface 44 of the switch base 40 may define keyed openings 48(FIG. 3) and the housing portion 20 b may include keys 28 that arereceived within the keyed openings 48 to longitudinally position and fixthe switch base 40 within the switch base cavity 27. The keys 28 may bereceived within the keyed openings 48 to seal a portion of the switchbase 40 (e.g., the proximal most keys 28 may seal the lower end of thebus openings 43. It is contemplated that the keys 28 may be slightlylarger than the keyed openings 48 such that when the keys 28 arereceived within the keyed openings 48 the keys 28 frictionally securethe switch base 40 within the switch base cavity 27. In addition, thekeys 28 also prevent fluid from entering the openings 43 and contactingthe prongs 52 and/or leads 19.

The membrane 60 also forms a fluid impermeable seal with the switch baseassembly 12 to prevent fluid from contacting the prongs 52, the switchcontacts 54, or other electrical connections of the switch base assembly12. The membrane 60 may be constructed of a flexible non-conductivematerial applied with adhesive on the side facing the switch base 40,which allows the actuator 70 to engage the switch contacts 54. Suitablenon-conductive materials include, but are not limited to, polymericmaterials, such as polyester films or ionically cross-linkedthermoplastics based upon ethylene copolymerised with carboxyl groupsand a metal ions. It is contemplated that the flexible membrane 60 is alaminate of materials including polyester for strength, a resin layerfor toughness, and an adhesive layer. It will be appreciated that theflexible membrane may be resilient, yet flexible to allow for deflectionof the switch contacts 54 without reducing the tactile feel of theswitch contacts 54.

The membrane 60 includes a top portion 62 that is disposed over the topsurface 42 of the switch base 40 and the power bus 50. The membrane 60may be adhered using adhesive and/or formed as a film over the switchbase 40 and the power bus 50 and allowed to dry and adhere thereto. Thetop portion 62 may be adhered to the top surface 42 of the switch base40 and/or the power bus 50. The membrane 60 includes side portions 64that extend from the top portion 62 towards the bottom surface 44 of theswitch base 40 to form a fluid impermeable seal with the side surfaces46 of the switch base 40. The side portions 64 may be adhered to theside surfaces 46 of the switch base 40 and/or the power bus 50. Inembodiments, the membrane 60 may include bottom portions (not shown)that extend from the side portions 64 towards one another and form afluid impermeable seal with the bottom surface 44 of the switch base 40.The bottom portions (not shown) may be adhered to the bottom surface 44of the switch base 40.

With reference to FIG. 3, the housing portion 20 a defines a switchopening 29 in communication with an upper portion 27 a of the switchbase cavity 27. An actuator 70 is disposed within the switch opening 29.The actuator 70 may be a rocker switch that rocks (e.g., pivots) withinthe switch opening 29 to activate switch contacts 54 as described above.Alternatively, the actuator 70 may be one or more push buttons (notshown) positioned within the switch opening 29. It will be appreciatedthat fluid may ingress through the switch opening 29, switch ingressI_(S) (FIG. 3), into the upper portion 27 a of the switch base cavity27.

With reference to FIG. 3, the pencil 10 includes features (e.g.,membrane 60 and proximal and distal upper bulkheads 66, 68) to preventthe fluid ingressing through the switch opening 29 (e.g., switch fluidingress I_(S)), through the proximal opening 22 (proximal fluid ingressI_(P)), and through the distal opening 38 (e.g., distal fluid ingressI_(D)) from contacting electrical components within the switch basecavity 27. The tortuous path 21 includes a plurality of bulkheads (e.g.,bulkheads 25, 32, 34, 65, 66, etc.) that limit fluid ingress into theswitch base cavity 27, such that in instances in which any fluid thatpenetrates through the bulkheads is retained in compartments definedtherebetween in the tortuous path 21.

In particular, when the switch base assembly 12 is disposed within theswitch base cavity 27 of the tortuous path 21, portions of the tortuouspath 21 engage the membrane 60 to form a fluid impermeable seal with themembrane 60 to prevent fluid from contacting the prongs 52, the switchcontacts 54, or other electrical connections of the switch base assembly12. With particular reference to FIG. 3, the first housing portion 20 aincludes proximal and distal upper bulkheads 66, 68 that extend downwardtowards the second housing portion 20 b. The proximal upper bulkhead 66are positioned adjacent a proximal end of the switch opening 29 and thedistal upper bulkhead 68 are positioned adjacent a distal end of theswitch opening 29. The proximal and distal upper bulkheads 66, 68 engagethe membrane 60 to form a fluid impermeable seal with the membrane 60 toprevent fluid from contacting the switch contacts 54 or electricalconnections of the switch base assembly 12. Additionally, the proximaland distal upper bulkheads 66, 68 compress the membrane 60 against theswitch base 40 and/or the power bus 50 to form a fluid impermeable seal.The second housing portion 20 b includes a plurality of proximal lowerbulkheads 65, which extend upward toward the first housing portion 20 a.The proximal lower bulkheads 65 engage the bottom surface 44 of theswitch base 40 to prevent fluid from contacting the switch contacts 54or electrical connections of the switch base assembly 12.

First and second housing portions 20 a and 20 b also include a switchbase bulk head 26, a cable bulkhead 25, and a proximal opening bulkhead23 to prevent proximal fluid ingress I_(P) from reaching proximalportion 27 c of the switch base cavity 27. More specifically, the sheath17 of the cable 14 forms a fluid impermeable seal with each of theproximal switch base bulkhead 26, cable bulkhead 25, and the proximalopening bulkhead 23. The proximal opening bulkhead 23 is positionedadjacent the proximal opening 22 to prevent proximal fluid ingress I_(P)through the proximal opening 22 from contacting electrical componentswithin the switch base cavity 27. The power cable bulk head 25 ispositioned between the proximal opening 22 and the proximal switch basebulk head 26 to further prevent proximal fluid ingress I_(P) through theproximal opening 22 from contacting electrical components within theswitch base cavity 27.

In embodiments, the tortuous path 21 also includes a distal openingbulkhead 36 positioned adjacent the distal opening 38 to further preventdistal fluid ingress I_(D) (FIG. 3) through the distal opening 38 fromcontacting electrical components within the switch base cavity 27. Incertain embodiments, the tortuous path 21 includes an electrode bulkhead34 positioned between the distal lower bulkhead 32 and the distalopening 38 to further prevent distal fluid ingress I_(D) (FIG. 3)through the distal opening 38 from contacting electrical componentswithin the switch base cavity 27. In further embodiments, the tortuouspath 21 also includes a distal lower bulkhead 32, which seals the switchbase cavity 27 to prevent distal fluid ingress I_(D) (FIG. 3) throughthe distal opening 38 from contacting electrical components within theswitch base cavity 27.

Referring to FIGS. 2 and 3, the assembly of the pencil 10 is detailed inaccordance with the present disclosure. The switch base assembly 12 isassembled by coupling the power cable 14 to the switch base 40, couplingthe power bus 50 to the switch base 40, and adhering the membrane 60 tothe switch base 40. The leads 19 of the power cable 14 are inserted intothe connector opening 45 in the proximal end surface 49 of the switchbase 40 to couple the power cable 14 to the switch base 40. Each of theprongs 52 is electrically coupled to a respective one of the leads 19when the prongs 52 are inserted into the bus openings 43.

To couple the power bus 50 to the switch base 40, the prongs 52 areinserted into the bus openings 43 defined by the top surface 42 suchthat each of the prongs 52 is in electrical communication with one ofthe leads 19 and the electrode contact 58 extends distally from the topsurface 42 of the switch base 40. In embodiments where the power bus 50includes side protrusions 53, the side protrusions 53 are receivedwithin the cutouts 47 in the side surfaces 46 of the switch base 40. Theside protrusions 53 may assist in aligning and positioning the power bus50 relative to the switch base. The side protrusions 53 may be portionsof the switch contacts 54 that are disconnected from the power bus 50adjacent the bus openings 43 after the power bus 50 is installed and theelectrical connects are made between the leads 19 and the prongs 52.

With the power bus 50 coupled to the top surface 42 of the switch base40, the membrane 60 is adhered to the switch base 40 to seal the topsurface 42 of the switch base 40 and the power bus 50. The membrane 60may be adhered to the top surface 42 of the switch base 40 over thepower bus 50. Additionally or alternatively, the membrane 60 may extendfrom the top surface 42 over a portion of the side surfaces 46 and maybe adhered to the side surfaces 46. In some embodiments, the membrane 60may extend over each side surface 46 and portions of the membrane 60 mayextend over a portion of the bottom surface 44 and may be adhered to thebottom surface 44. Additionally, the membrane 60 may extend overportions of the power cable 14.

With the switch base assembly 12 assembled, the switch base assembly 12is secured within the switch base cavity 27. The switch base assembly 12is aligned with the second housing portion 20 b such that the switchbase 40 is positioned in the lower portion 27 b of the switch basecavity 27 defined by the second housing portion 20 b. The proximal endof the switch base 40 may engage the proximal switch base bulkhead 26 orthe distal end of the switch base 40 may engage the distal lowerbulkhead 32. Additionally or alternatively, each of the keys 28 of thesecond housing portion 20 b engage a respective keyed opening 48 definedin the bottom surface 44 of the switch base 40 to align the switch base40 with the second housing portion 20 b. The sheath 17 of the powercable 14 is positioned in the tortuous path 21 passing through theproximal opening 22. The sheath 17 may pass through and form a fluidimpermeable seal with each of the proximal switch base bulk head 26, thecable bulkhead 25, and the proximal opening bulkhead 23. The electrodeconnector 58 may pass through and form a fluid impermeable seal witheach of the distal lower bulkhead 32 and the electrode bulkhead 34.

The first housing portion 20 a is positioned over the second housingportion 20 b and the switch base assembly 12 such that the switch baseassembly 12 is aligned with the upper portion 27 a of the switch basecavity 27 defined by the first housing portion 20 a. The actuator 70 ispositioned between the first housing portion 20 a and the switch baseassembly 12. The actuator 70 is pressed into the first housing portion20 a such that the actuator 70 is pivotally coupled to the first housingportion 20 a. The actuator 70 may be pressed into the first housingportion 20 a before the first housing portion 20 a is positioned overthe first housing portion 20 a and the switch base assembly 12.

Next, the first housing portion 20 a is pressed over the switch baseassembly 12. The proximal and distal upper bulkheads 66, 68 extendingfrom the first housing portion 20 a engage the membrane to form a fluidimpermeable seal with the membrane 60 to prevent fluid ingressing intothe upper portion 27 a of the switch base cavity 27 through the switchopening 29 from contacting the switch contacts 54 or other electricalconnections of the switch base assembly 12. Additionally, the proximaland distal upper bulkhead 66, 68 may compress the membrane 60 againstthe switch base 40 and/or the power bus 50. The first housing portion 20a is pressed over the switch base assembly 12 until the mating surfaces24 a, 24 b of each of the first and second housing portions 20 a, 20 bin contact with one another. The first and second housing portions 20 a,20 b are then coupled together in a sealing relationship by applyingadhesive, sonic welding, laser welding, or any other suitable methods.

With the first and second housing portions 20 a, 20 b coupled together,fluid is prevented from contacting portions of the switch contacts 24and the electrical connections of the switch base assembly 12. The lowerportion 27 b of the switch base cavity 27 is sealed in a fluid proofmanner by at least the membrane 60, the proximal switch base bulkhead26, the distal lower bulkhead 32, and the second housing portion 20 b.

It is contemplated that the assembly of the pencil 10 as detailed hereinmay be completely automated (i.e., without the need for hand laborduring the assembly).

It is contemplated that fluid may enter the pencil 10 through the switchopening 29 into the upper portion 27 a of the switch base cavity 27defined by the first housing portion 20 a, the proximal opening 22, andthe distal opening 38. As such, the membrane 60 is positioned to preventfluid that enters the pencil 10 through the switch opening 29 frompenetrating the lower portion 27 b of the switch base cavity 27 andcontacting the switch contacts 54 and other electrical connections ofthe switch base assembly 12. The proximal switch base bulkhead 26prevents fluid that enters the pencil through the proximal opening 22from penetrating the switch base cavity 27. In addition, the proximalopening bulkhead 23 or the cable bulkhead 25 may prevent fluid thatenters the pencil 10 through the proximal opening 22 from penetratingthe switch base cavity 27. The distal lower bulkhead 32 prevents fluidthat enters the pencil 10 through the distal opening 38 from penetratingthe switch base cavity 27. In addition, the electrode bulkhead 34 andthe distal opening bulkhead 36 may prevent fluid that enters the pencil10 through the distal opening 38 from penetrating the switch base cavity27.

While several embodiments of the disclosure have been shown in thedrawings, it is not intended that the disclosure be limited thereto, asit is intended that the disclosure be as broad in scope as the art willallow and that the specification be read likewise. Any combination ofthe above embodiments is also envisioned and is within the scope of theappended claims. Therefore, the above description should not beconstrued as limiting, but merely as exemplifications of particularembodiments. Those skilled in the art will envision other modificationswithin the scope and spirit of the claims appended hereto.

What is claimed:
 1. A surgical instrument comprising: a switch basehaving a top surface, a bottom surface, and side surfaces; a power buscoupled to the switch base; at least one electrical lead coupled to thepower bus; a membrane disposed over at least the top surface of theswitch base and over the power bus sealing the top surface of the switchbase; and a housing defining a proximal end, a distal end, and a switchbase cavity between the proximal and distal ends, the housing includinga plurality of bulkheads forming a plurality of fluid impermeable sealswithin the housing and disposed adjacent to at least one of the proximalend or the distal end, a first bulkhead of the plurality of bulkheadsforming a proximal fluid impermeable seal proximal of the switch basecavity configured to deter fluid from penetrating a proximal portion ofthe switch base cavity within which the at least one electrical lead iscoupled to the power bus, wherein the plurality of bulkheads includes aproximal bulkhead extending from the housing and engaged to a portion ofthe membrane that is disposed over a proximal end portion of the switchbase.
 2. The surgical instrument of claim 1, wherein the membrane isdisposed over the top surface and a portion of each of the side surfacesof the switch base.
 3. The surgical instrument of claim 2, wherein themembrane is disposed entirely over each of the side surfaces andportions of the membrane are disposed over portions of the bottomsurface of the switch base.
 4. The surgical instrument of claim 1,wherein the membrane and the plurality of bulkheads prevent a fluid fromcontacting with the switch base.
 5. The surgical instrument of claim 1further comprising a cable enclosing at least one electrical lead, thecable passing through and engaged by the first bulkhead.
 6. The surgicalinstrument of claim 5, wherein the plurality of bulkheads includes aproximal opening bulkhead positioned proximally of the first bulkheadand adjacent the proximal opening which forms one of the plurality offluid impermeable seals with the cable.
 7. The surgical instrument ofclaim 1, wherein the housing includes distal upper and lower bulkheadsthat form a distal fluid impermeable seal.
 8. The surgical instrument ofclaim 7, wherein the distal upper and lower bulkheads form the distalfluid impermeable seal with the switch base.
 9. The surgical instrumentof claim 1, wherein the housing includes a first housing portion and asecond housing portion, the first and second housing portions joinedalong mating surfaces that are parallel to a longitudinal axis of thehousing.
 10. The surgical instrument of claim 9, wherein the firsthousing portion includes a first half of at least one of the pluralityof bulkheads and the second housing portion includes a second half ofthe at least one of the plurality of bulkheads.
 11. The surgicalinstrument of claim 1 further comprising an actuator operatively engagedwith the power bus, wherein the housing defines an actuator openingthrough an outer surface thereof, the actuator opening being incommunication with the switch base cavity and the actuator beingdisposed within the actuator opening.
 12. A surgical instrumentcomprising: a switch base having a top surface, a bottom surface, andside surfaces; a power bus coupled to the switch base; a membranedisposed over at least the top surface of the switch base and over thepower bus sealing the top surface of the switch base; and a housingdefining a proximal opening, a distal opening, an actuator opening, anda switch base cavity including an upper portion and a lower portion, thehousing including a plurality of bulkheads forming a plurality of fluidimpermeable seals within the housing and disposed adjacent to at leastone of the proximal opening, the distal opening, or the actuatoropening, the fluid impermeable seals configured to prevent fluid frompenetrating the switch base cavity, wherein the plurality of bulkheadsincludes a proximal bulkhead extending from the housing and engaged to aportion of the membrane that is disposed over a proximal end portion ofthe switch base.
 13. The surgical instrument of claim 12, wherein theplurality of bulkheads includes upper bulkheads extending from thehousing between the actuator opening and the proximal bulkhead, each ofthe upper bulkheads engaging the membrane to form one of the pluralityof fluid impermeable seals.
 14. The surgical instrument of claim 12,wherein the membrane is disposed over the top surface and a portion ofeach of the side surfaces of the switch base.
 15. The surgicalinstrument of claim 12, further comprising a cable enclosing at leastone electrical lead, the cable extending through the proximal opening ofthe housing, wherein the cable passes through and is engaged by theproximal bulkhead.
 16. The surgical instrument of claim 15, wherein theplurality of bulkheads includes a proximal opening bulkhead positionedproximally of the proximal bulkhead and adjacent the proximal openingwhich forms another of the plurality of fluid impermeable seals with thecable.
 17. The surgical instrument of claim 16, wherein the plurality ofbulkheads includes a distal lower bulkhead and an electrode connectorbulkhead disposed between the distal opening and the distal lowerbulkhead, each of the distal lower bulkhead and the electrode connectorbulkhead form one of the plurality of fluid impermeable seals with anelectrode connector extending proximally from the power bus.